Important points to remember about OSI – Application Layer
The Application layer of TCP/IP suite corresponds to combination of Application Layer, Presentation Layer and Session Layer of OSI Model. This article intends to discuss briefly the Application Layer of OSI model.
Application Layer is highest layer /7th Layer/Closest to user layer of 7 OSI layers.
Many people think that Application Layer will contain different applications. Application Layer does not contain any application. It contains the protocols supporting different applications.
If an application A has to work over networks, required data and related instruction needs to be sent. Here role of Application Layer comes into picture. Application layer sends the required data and related information to the protocol(s) supporting application A and not to the application A. In this way data and instruction is sent to lower layer and request is sent to the Presentation Layer(Layer 6).
Application Layer defines message types, message formats, semantics and rule sets for communication between user and application. Application layer also controls communication between application and user.
There can be two types of application layer protocols.
1.CASE
2.SASE
Some common protocols sitting in Application Layer are:
FTP
Telnet
SMTP
DNS
DHCP
Summary:
1. Application layer connects user and applications.
2. Application Layer helps in communication between different applications through protocols supporting those applications.
3. It controls the exchange of information.
4. Application layer handles semantic conversion between applications
5. File Transfer, Virtual filing, job/message transfer are also addressed by Application Layer.
Abbreviation Used:
TCP - Transmission Control Protocol
IP – Internet Protocol
OSI- Open System Interconnection
SMTP- Simple Mail Transfer Protocol
FTP- File Transfer Protocol
DNS- Domain Name service
CASE - Common Application Specific Elements
SASE- Specific Application Specific Elements
0 comments:
Post a Comment